The present invention relates to cable conduits and, more specifically, to flexible, semi-concentric cable conduits constructed of a single wire.
Conduits are used to protect and route actuation cables between service locations in a variety of applications. As defined herein, conduits are at least one wire, serpentine wound to a predetermined diameter, forming successive wire loops (or segments) wherein the wire of each loop abuts a wire in each successive loop, and a plurality of the wire loops form a hollow, flexible, tubular body.
A single-wire conduit system uses a serpentine-wound single wire, that in cross section has a generally rectangular shape. The wire winding loops abut each other when the conduit is in a straight or non-flexed position. The conduit is normally provided with a protective external jacket of a flexible, usually fluid-resistant material. A flexible, braided wire or cable (hereafter referred to as a cable) is normally run through the center of the conduit and extends from either end of the conduit. The cable is normally attached to an actuation device on a first end and to the item to be actuated on a cable second end. In many applications, a plastic, cylindrically shaped sleeve is disposed within the circular inner diameter of the conduit hollow tubular body to surround the cable.
A drawback of prior single-wire conduit results when bending the conduit. In cross section, the hollow, tubular body when bent forms an inside radial wall and an outside radial wall. The rectangular shaped conduit wire on the outside radial wall deflects creating gaps between successive coils. The forces required to flex the coils create or increase resistance to conduit bending. The gaps created between successive coils also create friction at the plastic sleeve interface and at the jacket interface which can damage the sleeve or jacket.
Known two-wire conduits have two primary disadvantages. First, addition of a second, round wire adds an additional material cost to the conduit system. Second, the round wire adds complexity to the manufacture of the conduit system, in that the round wire must be position controlled when wound into the conduit.
A need therefore exists for a single-wire conduit and conduit system that minimizes potential bending damage and the cable friction damage caused by known single-wire conduits when bent.
According to one aspect of the present invention, a conduit is formed by a wire circularly formed into a plurality of continuously abutted loop pairs. In cross section, the wire has a modified rhomboid shape cross section having approximately parallel sides, a rounded first end and a tapered second end. The plurality of continuously abutted loop pairs are continuously stackable forming a hollow tubular body having a centerline. The hollow tubular body is deformable in an arc about the centerline such that the rounded first end of the wire is both rotatable and translatable along the tapered second end of the wire in each loop pair.
In another aspect of the present invention, a method is provided to form a single-wire conduit. The method comprises the steps of (1) selecting a metal strip having a cross sectional shape having approximately parallel sides, a rounded first end and a tapered second end; (2) serpentine winding the metal strip into a hollow tubular body having a plurality of wire loops combining to form approximately parallel abutting wire loop pairs; and (3) aligning the metal strip such that the rounded first end is in continuous, displaceable contact with the tapered second end for each wire loop pair.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.